This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The incidence of type 2 diabetes in children has increased dramatically in the past decade. With earlier onset and thus longer duration of disease these children will have increased health care costs;they may also have more complications than someone diagnosed in middle age. There is little published experience on the best treatment to maintain normal glycemia and prevent complications in children with type 2 diabetes. This trial will determine which of 3 treatments is most effective in maintaining glycemic control. Although the trial will not be long enough to assess if there is a significant difference in complications between these 3 arms, surrogate markers associated with complications will be measured (e.g., lipid profile, C-reactive protein, microalbuminuria). This is a prospective, partially double-blinded, randomized clinical trial with 3 treatment arms: metformin alone, metformin plus intensive lifestyle treatment (behavior modification program). The primary endpoint is time to failure defined as hemoglobin A1c>or =8% for 6 or more consecutive months. Subjects will be seen every 1 to 4 weeks during the 2-6 months of the runnin. After randomization, subjects will be seen every 2 months in the first year and every 3 months in subsequent years. In addition, subjects in the lifestyle arm will meet with a PAL (physical activity and nutrition leader) once a week for the first 6 months, every 2 weeks in the 2nd 6 months and monthly thereafter. Endpoint measurements will be done at randomization, 6 months, 24 months and end of study. The primary objective of the TODAY trial is to compare the efficacy of the three treatment arms on time to treatment failure based on glycemic control. The secondary aims are to: compare and evaluate the safety of the three treatment arms;compare the effects of the three treatments on the pathophysiology of T2DM with regards to beta cell function and insulin resistance, body composition, nutrition, physical activity and aerobic fitness, cardiovascular risk factors, microvascular complications, quality of life, and psychological outcomes;evaluate the influence of individual and family behaviors on treatment response;and compare the relative cost effectiveness of the three treatment arms.